Display’s built-in test
Best option. Many monitors and laptops can show their own solid colors without the browser, cable, or graphics hardware.
Dell monitor exampleCheck the screen itself
Check whether the mark comes from the screen or from the image being sent to it.
The key idea
A problem in the screen itself stays in the same place during the display’s built-in test or no-signal screen. A problem caused by an app, cable, input, or computer may move, disappear, or appear in screenshots.
Use the strongest check available
Three ways to tell where the mark comes from.
No-signal screen
For an external monitor, disconnect the video cable while leaving power connected. If the mark remains on the monitor’s own message or background, the cable or connected device is less likely to be the cause.
Screenshot check
Take a screenshot and view that file on a different screen. If the mark appears in the file, investigate software, overlays, the GPU, or content.
Do not press, rub, or massage the screen.
Current Dell guidance explicitly advises against DIY pressure or pixel-fixing software for covered products. Protect your return and warranty options before experimenting.
Manufacturer guidance
Policies vary by model and region.
- Apple — LCD pixel anomalies
- Dell — display pixel guidelines
- Dell — built-in monitor diagnostics
- EIZO — monitor test
- LG — OLED pixel cleaning
- Apple — OLED image persistence
- Dell — laptop LCD built-in self-test
- Dell — LCD light leakage guidance
- Sony — OLED panel refresh guidance
- Samsung — screen cleaning guidance
- W3C — flashing-content safety